A Volcanic Labyrinth

Posted 01.03.13

NOVA

Thrihnukagigur crater is the only place on Earth where the anatomy of a volcano can be studied from the inside. When geologists journeyed into its heart, they discovered that a network of fissures links together distant volcanoes.

Transcript

Doomsday Volcanoes

NARRATOR: After squeezing through the neck, they're confronted with an amazing sight: …

SIGRUN HREINSDÓTTIR (University of Iceland): Wow! Look at that.

FREYSTEINN SIGMUNDSSON: Yeah. It's beautiful.

NARRATOR: … a vast chamber, dropping 450 feet below the surface. Four thousand years ago, when the magma drained, the chamber remained remarkably intact. It's the only place on Earth where scientists can study a volcano from the inside.

FREYSTEINN SIGMUNDSSON: Amazing.

NARRATOR: Freysteinn is looking for evidence of how volcanoes like this are fed by molten rock. It's been something of a mystery, until now.

FREYSTEINN SIGMUNDSSON: Look at this. Can you see the fracture?

SIGRUN HREINSDÓTTIR: Wow. It's actually really cool how it goes up.

FREYSTEINN SIGMUNDSSON: This is an absolutely unique place. It is fantastic. We can see the fissures that fed magma into this volcano. This black line in the wall, it's a crack that delivered magma to the eruption. Now the magma is solidified in this fissure.

NARRATOR: This fissure acted like a giant vein, pumping magma into the chamber horizontally, as well as from deep below.

FREYSTEINN SIGMUNDSSON: What is so special is we can clearly see it, both sides.

NARRATOR: The fissure sliced right through the chamber and out the other side, and Freysteinn is working out which direction it took.

FREYSTEINN SIGMUNDSSON: If you trace it, you get the orientation of this crack.

NARRATOR: By lining up the fissure on either side of the chamber, the team finds the exact route it took and make an important discovery.

FREYSTEINN SIGMUNDSSON: What we have found is that they can go on for many miles. They're like thin sheets. They can link different volcanoes.

NARRATOR: So, although volcanoes appear isolated on the surface, fissures carrying magma, can link them underground. And that's an important consideration in trying to predict which of Iceland's volcanoes might erupt next.

Additional funding for this program is provided by Millicent Bell, through the Millicent and Eugene Bell Foundation.

National corporate funding for NOVA is provided by Draper and 23andMe.
Major funding for NOVA is provided by the David H. Koch Fund for Science, the Corporation for Public Broadcasting, and PBS viewers.